Methods for detecting analytes by haemagglutination as well as particle agglutination tests are known. Methods are known for haemagglutination, wherein haemagglutinates are separated by a centrifuging step, through an inert matrix, from individual non-agglutinated erythrocytes (e.g. EP-A-0194212, EP-A-0305337, EP-A-0485228, EP-A-0725276). According to this method, agglutinated erythrocytes are retained on or in the inert matrix and can thus be separated from non-reacting individual erythrocytes, which may pass through the matrix and may deposit on the bottom of the reaction vessel.
The separation matrices are normally porous matrices (for example made of glass); gel bead matrices (for example of SEPHADEX®, SEPHACRYL®, AGAROSE®: EP-A-9184212, EP-A-0305337) or glass bead matrices (EP-A-0725276).
All these systems have in common that the separation matrix and the carrier element system comprise two separate components. The same applies to likewise disclosed methods, wherein, instead of beads, porous or filter matrices are used. The carrier element system is manufactured, as the case may be, by conventional (macro) injection molding methods.
The aforementioned matrices are used in blood group serological diagnostics, in particular for the visualization of haemagglutination reactions. They generally detect parameters, which are of importance in particular with regard to transfusions or the morbus haemolyticus neonatorum. In this context, this concerns inter alia the detection of antigens on the surface of those erythrocytes which are characteristic of the blood groups. Further important antigen systems are also to be found on thrombocytes, granulocytes, lymphocytes, which likewise play a role in transfusions and/or transplantations. Moreover, haemagglutinating viruses may be detected in a similar manner.
The aforementioned matrices, in particular gel bead matrices, are used for particle agglutination tests as well. However, to date only synthetic particles are used, meeting tight specifications, in particular having a high specific density and a lower diameter than erythrocytes (e.g. specific density >/=1.1; diameter <5 μm; cf. EP-0849595).
The prior art methods present a number of drawbacks. Although a spatial separation of haemagglutinated and individual erythrocytes is obtained by centrifuging, the reaction matrix for positive and negative reactions, however, comprises a single compartment, so that the passage from negative (non-agglutinated) to positive (agglutinated) reactions is fluid and the evaluation of the results is thus subject to a certain subjectivity. Particularly in the case of slightly positive reactions, the indistinct demarcation in relation to negative results may result in interpretation difficulties. Furthermore, the reproducibility of the known methods, functioning, in particular, with a gel bead matrix, depend considerably on the matrix quality, normally polyacrylamide. These gels differ from one charge to the other, resulting in detection reactions which differ considerably in intensity of detection in the same sample. This makes it more difficult to standardize and reproduce the results. The sensitivity of the gel particles in relation to any type of shear forces resulting, in particular, in broken gel particles, is a further problem, which may lead to distorted reaction results. In addition, all matrices mentioned here have in common that they are three-dimensional and that a large component of the matrix space consists of matrix polymers, resulting in part of the colored particles, enclosed in the matrix, remaining invisible to the naked eye, i.e. not being able to contribute to detection. Furthermore, these methods are little suited for detecting thrombocyte properties in intact thrombocytes, since thrombocytes do not pass very well through the gel.